Intercept operator&#39;s position for unassigned party line stations



W. HATTON INTERCEPT OPERATORS POSITION FOR UNASSIGNED PARTY'LINE STATIONS Au@ ze, 1947.

Filed Mrch 12, 1945 5 sheets-sheet 1 INVENTOR. W/L' MM #ATTO/V /NrfRrfPr//va 'FM/05H cer .HER GROUP af 20o L/Nfs.

Aug. 2e, 1947. 2 WHATTQN 2,426,210

INTERCEPT OPERATORS POSITION FOR UNASSIGND PARTY LINE STATIONS I N VEN TOR.

Aug.` 26, 1947.` w. HATTON INTEROEE'T OPERATOR'S POSITION FOR UNAssIGNED PARTY LINE- STATIONS Filed March 12, 1945 ssheets-sheet 3 Patented ug. 26, 1947 INTERCEPT OPERATORS POSITION FOR UNASSIGNED PARTY LINE STATIONS William Hatton, Maplewood, N. J., assigner to international Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application March 12, 1.945, Serial No. 582,195

16 Claims.

This invention relates to automatic telephone systems, and more particularly to such systems having party-line stations.

A principal object of the invention relates to an improved automatic telephone switching system of the kind in which lines provided with a plurality of party-line stations are connected to a single set of line terminals in the final selectors, as distinguished from those systems employing a set of line terminals per station.

Another principal object is to provide an improved method of discriminating between partyline stations served by a common line, and for notifying the calling subscriber when his connection to the called party-line station cannot be completed. This latter condition may for example arise when the called party-line station has been disconnected from service or when its original characteristic number has been or is being changed.

Another principal object is to provide an automatic switching system employing party-line stations with selective ringing, together with means for automatically connecting an intercept operators position to the extended calling line when the particular party-line station which is being called cannot be connected to in the normal way.

A feature of the invention is concerned with a novel switching control arrangement for partyline operation whereby connections to a desired -party-line station can be re-routed through a special finder switch associated with a group of final selectors. In this arrangement the partyline stations, for example i'ive in number, terminate in a common set of bank contacts in the final selector, and the said finder switch automatically hunts for the desired station which has been previously marked, in order that an intercept operators position may be connected to the talking circuit which has previously been established under control of the calling subscriber.

Another feature relates to an automatic intercepting arrangement for selective ringing party-line stations, whereby improved service flexibility is attained with a minimum of cross connection changes when a party-line designation is changed or being changed.

A further feature relates to a novel test circuit for party-line switching whereby a party-line can be conveniently marked, for example by a ground, when it is taken out of service or has an unassigned designation. As a result it is possible to employ in a final selector a terminal per line with a plurality or party-line stations effectively served by the same single set of terminals in the final selector, and still be able to discriminate as to those party-line stations which are taken out of service so that an intercept operators position can be automatically connected into circuit when such a station is being called.

A further feature relates to a novel line-finder control circuit arrangement.

A further feature relates to identification circuits for identifying lines in a ringing condition.

A still further feature relates to the novel organization, arrangement and relative interconnection of parts which cooperate to provide an improved automatic switching system having a plurality of party-line stations per set of final selector terminals.

Other features and advantages not specifically enumerated will be apparent after a consideration of the appended descriptions and claims.

Since the inventive concept is concerned primarily with the iinal selector stage of an automatic telephone switching system, only those parts of such a system are shown as are required to understand certain preferred modes of practising the invention.

Accordingly in the drawing,

Fig. 1 represents in schematic form the more important parts of a final selector switch customarily used in an automatic telephone switching system of the well-known rotary type.

Fig, 2 shows a typical line circuit with the usual cut-olf and line relays.

Fig. 3 represents the usual main distributing frame.

Fig. 4 represents a series of five party-line stations connected to the same telephone line terminating in a common set of bank contacts in the iinal selector.

Fig. 5 shows the special finder and test circuit for connecting an intercept operators position to the previously extended talking connection.

Fig. 6 shows a modification of the finder test circuit of Fig. 5.

While the invention will be disclosed herein as embodied in a system employing rotary power driven selectors, finders and sequence switches, it will be understood that in certain of its aspects, the invention is not limited thereto. Merely for explanatory purposes, therefore, the invention will be described in connection with an automatic switching system of the type described and illustrated in Electrical Communication, January 1925, pages 153-189, and the disclosure of which is expressly incorporated herein by reference. In order to maintain simplicity in the drawing only a single set of brushes and corresponding single set of bank contacts are shown for each of the rotary switches, it being understood that the various switches may have their bank contacts multiplied in known manner. Likewise, the particular sequence switch shown, has the requisite number of contact cams and associated sets of Ibrushes. Merely for simplicity, only ve cams and associated brush sets are shown, and the cams are designed to be rotated to the requisite number of positions, for example eighteen. The manner` of controlling the sequence switch associated with the iinal selector, and the manner of extending a calling line to the called line under control of the sequence switches and intervening selector switches are described insaiol Electrical Communication, January 1925.

In order to explain the novel features, it will be assumed that a. calling subscriber has dialled the designation of a party-line station. The party-lines may each be equipped for any desired number of stations perline, and for illustration they are shown as five `stationv lines. In practising the invention, the calledliney designation will have a suflix characteristic Yoi each party-line station, and each party-line station will be equipped with selectively responsive ringing equipment which responds to individual ringing frequency currents. Thus stations #l to #5 may be rung by res'pective'currents of 16, 25, 33, 50

and 56 C. P. S. The sequence switch associated with the iinal selector will remain, during the ringing condition, in one of the ve positions to 14, depending uponV which station suiiix or ring digit hasbeen dialled. The proper ringing frequency'may of course beselected in any known manner. Y

If the particular station which has been dialled, is out of service for any reason so that the usual answerback condition is not attained, it is necessary to connect an intercept operators position to the extended talking connection, and since all five stations are connected to the same set of nal bankv contacts, it becomes necessary to make sure that the operator is signalled only when an out of service party-line station/hasfbeen dialled. Assume therefore, for illustration,V thatv the particular party-line shown `in the drawinghas been dialled and with a suilx for station #3, and that said station is out of service orY assume that the dialleddesignation' is assigned. Under those conditions the sequence swtch'of the iinal selector will stop for ringing, in position twelve and the circuit for applying the characteristic ringing current of 33 C. P. S. is closed at cam T. Moreover, a circuit is established for the answer back timing relay I0 traceable from battery, through the winding of relay IB', upper left and lower right brushes of sequence cam X to a ten-second timing contact on a common timing device T of any known kind. This timed interval may be of any desired duration greater than the average called subscribers Vanswering time.` After ten seconds a 400 C. P. S. low level current is applied over conductor II, lefthand contact set of relay I D, test brush c, thence to the c conductor of the called line. At the same time ground is extended through the righthand contacts of relay Ill, through the winding of relay I2'to battery. Relay I2 then'applies ground through its lefthand contacts, the righthand back contact set of re lay I3, conductor I4, winding of line finder power clutch magnet '|5, to battery. In accordance with the invention, there is provided one such line nder per group of 200i`1nal line circuits.

4 Thus each nder will serve 1000 party-line stations. It should be observed that the 400 C. P. S. current is of insulicient level to operate the lin cut-oli relay I6.

The finder bank contacts are arranged in eight rows with a corresponding set of eight rotatable brushes a to h. The a, b and c rows of xed contacts are co-nnected respectively to thei-lxed contactsof the iinal selector bank via conductors Il, I8 and I9. The ve remaining contacts of each set of eight are alotted respectively one to each of the ve party-line stations. W'hen a station is out of service, the corresponding one of these five contacts in the nder bank is grounded. In accordance with the invention, this grounding may be effected directly at the nder switch without disturbing the connections at the main distributing frame (Fig. 3).

Since the 400 C. P. S current is applied through the c brush of the final selector it is also applied to the corresponding c terminal of the nder. Consequently, whenyduring the hunting movement of the finder, its c brush engages the bank contact to which conductor I9 is connected, the 400 C. P. S. current isapplied through the righthand contact set of relay I2, thence through the input transformer 20 of grid-controlled amplier tube 2|, the plate circuit yof which is supplied with positive potential in series with the winding of relay I3, which thereupon operates. Relay I3 therefore breaks the foregoing described circuit for the nder power magnet I5 and the iinder comes to rest. At the same time a circuit is closed from battery, through the winding of relay 22, righthand front Contact and armature of relay I3, to ground at the lefthand contacts of relay I2. l When relay 22 operates in the last described circuit, it extends the d, e, f, g and h brushes'of the nder to corresponding relays 23 to 21. Since it has been assumed that the party-line station #3 and #5 are unassigned or out of service, the finder brushes f and IL are grounded,fthus closing operating circuits for the corresponding relays 25 and 2l. Relays 25 and 21 therefore connect the windings ci the tuned A. C. relays 28, 29, in parallel to the conductors I'I, I8. Since it has been assumed that the call- `ing subscriber dialled the designation of station #3 and the sequence switch is still in position I2, only the 33 C. P. S. current is Yapplied through the upper lefthand contact' of cam T, upper righthand contact of'camnS, winding of relayV SB, b brush Vandcor'responding fixed bank contact of the nal selector, conductor I8, brush b and corresponding xed bank contact of the finder, condenser 3I',righthand contacts of relay 25, winding of relay 28, lefthand contacts of relay 25, conductor I'I, a'brushes of the finder and final selector, to ground throughr the'upper right and lower right brushes of cam U. Relay V28 operates and applies ground tothe winding of relay 32 which locks through its lower contacts to ground at the normally closed ycontacts of the jack 33 at the intercept operators position. At the same time ground is extended through the upper front contact andv armature of relay 32 to the signal lamp 34 at the operators position corresponding to jack 33. The lighting of lamp 34 provides the intercept operator ,with asignal that the calling subscriber hasl dialled a connection to an Aunassigned party-line station. AThe operator thereupon plugs her talking setinto jack 33, whereby the sequence switch is advanced to position- I5 wherein the talking conductors aand b are completed betweenthe operators set and the calling subscriber. The operator then informs'the calling subscriber of the condition. If the party-line station which is desired 4by the calling subscriber has another number assigned to it, the operator communicates the new designation to the calling subscriber, instructiong him to replace his receiver and then dial the new designation.

When the calling subscriber dials the number corresponding to an assigned party-line station in service for example station #5, the sequence switch stops in position 14 and 66 C. P. S., ringing current is applied to the selective ringing equipment at station #5. However, if the called party does not reply within ten seconds, relays I0, I2, I3 and 22, operate as above described. It should be observed that relay 35 is slow-to-operate. So that if an unassigned number is called, relay 32 will operate and open the energizing circuit of relay 35 before the latter relay can operate its contacts. When calling an assigned number and the subscriber answers late, relays I2, I3, 22 energize, but since none of the relays 23 to 2l is energized, relay 32 is not operated. Therefore, relay 35 operates and completes the following alternative circuit for magnet l5. Since station is assigned, there will be no ground on its corresponding terminal h in the finder bank, and therefore neither relay 21 nor relay 29 will operate. With relays IB, l2, I3 and 22 in operated condition, a circuit is closed from battery through the winding of relay 35, outer left contacts of relay 22 to ground at the upper back contacts of relay 32. When relay 35 finally operates, a circuit is closed from the battery through the nnder power magnet I5, contacts of relay 35, the front contact and armature of relay I3 to ground at the lefthand contacts oi relay I2. This causes the finder to be driven from the particular called line and the power driving circuit remains closed until relay I3 releases. If finder starting relay I2' is still energized, the iinder will continue to rotate, and if there are no other party-lines being rung in the group served by the nder, the iinder will eventually return to the terminals from which it commenced its rotation. However, during its rotation, it passes over all the lines in the group which it serves, and therefore there is no possibility of the iinder being unduly delayed as would be the case if its rotation were contingent upon the called party answering or if its motion were delayed for the average answering time before a no-answer condition arises.

When the called party answers, the sequence switch is advanced to position I5 which is the talking position and the talking conductors d and b` are then completed through suitable cams (not shown) in the final selector sequence switch and thence through the previous switching stages represented schematically by the block 3B, to the calling subscriber station 31. When the conversation is terminated, the various switches are released in the well-known manner, for example as described in Electrical Communication, January 19125, pages 153-189. It will be noted that when the connection is completed to an assigned number station, the equipment shown in Fig. 5 is disconnected from the a and bY Wires of the established connection, and there is no possibility of interference and n o additional transmission losses are introduced into the line. On the other hand, if the connection is to an unassigned station, the tuned relays 28, 29, 38, 39, and d0, are bridged across the line and correspond to the respective ringers `at the partyline stations which would normally be across the line if all stations were in use. Consequently, substantially the same terminating conditions, so far as the ringing currents are concerned, are provided regardless of whether the party-line has one or more stations unassigned or out of service.I

Instead of employing separate relays 23 to `2'1 to control the connection of the associated tuned relays to the line, these relays may be connected in parallel to a pair of conductors 4|, 42 (Fig. 65. These conductors are connected to the inner front contacts of relay 22, so that when that relay operates in the manner above described, the five tuned relays are bridged across the a and b wires simultaneously and only that particular tuned relay will operate which corresponds to the called party-line station which is unassigned or out of service and which is represented by a ground at the corresponding bank contact d to h of the nder. This ground at the finder bank contact, instead of operating a corresponding relay such as the relays 23 to 21 (Fig. 5), is extended through the contacts of the particular tuned relay which is operated so as to cause the operation of relay 32 in exactly the same manner that relay 32 is operated by the grounded connection at the contacts of the tuned relays of Fig. 5. As soon as relay 32 operates, it causes the signalling lamp 34 to be lighted at the intercept operators position as above described. The remaining parts of Fig. 6 which bear the same designation numerals as the corresponding parts of Fig. 5 operate in the same manner as already described, and further description thereof is not believed necessary.

Various changes and modifications may be made in the disclosed embodiments without deof lines, and means for causing said identification nder switch to hunt for said wanted line if a subscriber on said wanted line does not respond to the ringing signal within a ygJredetermined time interval.

2. In an automatic telephone switching system, a group of subscribers lines comprising party lines with assigned and non-assigned party-line stations, means for extending a calling line to a wanted line in said group, means for applying a distinctive ringing signal to said wanted line characteristic of the dialled designation of a called party-line station on said line, an identiii cation finder switch having a set of bank terminals multipled to said group of lines, means for moving said switch to the terminals of said wanted line if a subscriber on said line does not respond within a predetermined time interval, means for arresting said nder switch in that position if the ringing signal corresponds to an unassigned party-line station, and means for causing said iinder switch to pass over the terminals in that position if the ringing signal corresponds to an assigned party-line station which does not answer. Y

3. In an automatic telephone switching system of the type having a final selector with a plurality of party-line stations served by a single set of bank contacts in the selector, means to establish a telephone connection through said selector to a common line leading to said stations, means to apply selective frequency ringing currents to said line, an automatic switch and a party line test mechanism common to a plurality of sets of said bank contacts, said party line test mechanism being controlled by said ringing currents transmitted over said automatic switch for determining the rcondition of said stations, and means responsive to the setting of said test Vmechanism for producing a supervisory signalwhen the dialled party-line designation corresponds to one of said stations which is unassigned.

4. In an automatic telephone switching system of the ytype lhaving a final switch with a plurality of party-line stations served by a single set of bank contacts in said switch and signalled by selective ringing currents, means controlled by a dialled party-line designation to extend a telephone connection through said contacts to a common line leading to said stations, an automatic switch and a party-line test mechanism common to a plurality of sets of said bank contacts, means responsive to the said extension to said common line to control the operation of said automatic switch to connect said test mechanism to the extended connection, said test mechanism having a plurality of members each responsive to a corresponding selective ringing current assigned to the party-line stations, means effective when said automatic switch connects said test mechanism with the said common line to cause the operation of only that one of said members which corresponds to the dialled party-line designation representing an unassigned station, and means controlled by said operated member for producing a supervisory signal indicative of the unassigned condition of the dialled party line designation.

5. In an automatic telephone switching system of the type having a final switch with a plurality of party-line stations served by a single set of bank contacts in said switch and signalled by selective ringing currents, a finder switch having a plurality of sets of bank contacts each set having certain contacts multipled to the corresponding bank contacts of said final switch and other contacts equal in number to the maximum number of party-line stations per line, means to apply a distinctive marking condition to each of said other contacts which represent unassigned partyline designations, means responsive to the seizure of a called line by said nal switch to start said iinderhunting for said terminals that are multipled to the seized line, a test mechanism associated with said nder to test for said marking condition on said other `contacts and for stopping said finder when -the multipled seized line terminals are found, and means responsive to the setting of said test mechanism for producingl a supervisory signal indicative of the unassigned condition of the dialled party-line designation.

6.In a telephone switching system, a called line having a plurality of party-line stations thereon and arranged to be signalled by selective fre.. quency ringing currents, a finder switch having at least one set of bank contacts with certain con'- tacts of the set multipled to said called line and with other contacts of the set having a distinctive marking potential for identifying party-line stations with unassigned numbers, means responsive to the extension of a connection to said called line for starting said nder to hunt for said multipled contacts, means to associate a test potential with said called line to stop said finder on said called line multiple contacts, a plurality of frequency responsive relays associated with said finder, means to apply selective frequency ringing currents to said called line and to said relays, and means controlled jointly by said marking potential and said relays for producing a supervisory signal to indicate that the particular dialled party-line designation is unassigned.

'7. An automatic telephone switch system including a calling line, a called line, a plurality of party-line stations served by said called line, each station having normally a distinguishing dialling designation wherein the station is identified by a corresponding suflix, means responsive to a dialled designation for extending the calling line to the called line, means effective when the called line is seized to apply a test signal thereto, a finder switch having a set of bank contacts with certain contacts multipled to the called line terminals and other contacts arranged to be grounded to identify those party-line stations Which have unassigned dialling designations, means controlled by said test signal to start said finder hunting for said multipled terminals, means to apply a'distinctive current to said multipled terminals in accordance with the suffix of the designation which has been dialled by the calling subscriber, a relay associated with said finder and responsive to said distinctive current, an intercept operators position, and means to signal said operator in response to the operation of said relay.

8. An automatic telephone switching system according to claim '7 in which the means for eX- tending the calling line to the called line includes a final selector switch and a sequence control switch which is arranged to selectively stop in any one of a series of positions for applying correspending selective ringing current to the called line, and said relay is connected through said finder to said sequence switch to respond to the particular frequency ringing current which is applied'.

9. An automatic telephone switching system according to claim 7 in Iwhich said relay is one of a set of relays equal in number to the total number of party-line stations to be served by the called line, and means are provided for connecting said relays simultaneously to the said multipled contacts in said nder.

l0. An automatic telephone switching system according to claim '7 in which said test signal is a low level frequency which is different from the frequencies of said selective ringing currents, and said nder is provided with an amplier for amplifying said test signal to control the stopping of said finderwhen the called line is found.

11. A line finder arrangement for party-station systems lcomprising a finder switch having its bank Vcontacts connected t0 lines to be found, means to apply a test potential to one of said terminalsto mark a line to be found, means to start said finder hunting for said one of said terminals, the bank contacts of said finder being arranged in sets with certain contacts connected to said lines and other contacts arranged to have special identifying potential applied thereto to control a supervisory signal when certain partystation designations have been dialled, said finder having a set of brushes equal in number to the number of contacts in each of said sets of bank contacts, a set of test relays corresponding to the total number of party-line stations on a line to be found, means to connect said relays to the finder brushes when the said marked line is found, and means under control of said finder for applying selective operating currents to said relays to cause only those relays to respond which correspond to the dialling of party-line designations which are'unassigned.

12. A line finder arrangement according to :claim 11 in which said relays are of the tuned type and respond selectively to party-station se lective ringing currents, and an additional set of relays are interposed between the said tuned relays and the finder brushes, said additional relays responding to said finder bank contacts which are grounded so as t close circuits only to the corresponding tuned relays.

13. A line finder arrangement according to claim 11 in which said relays are of the tuned type and respond selectively to party-station selective ringing currents, and another relay is provided and responds to the finding of the marked line to connect all said tuned relays simultaneously to the found line to receive selective ringing current.

14. A party-line automatic switching system including a calling line, a called line, having a plurality of party-line stations with respective selective ringing equipment, a finder switch responsive to the extension of a switching connection to said called line to start said finder hunting for the called line, a set of relays associated with said finder and responsive selectively to different ringing currents, an intercept operators position, means responsive to the operation of any one of said set of relays for displaying a signal at said position, and means effective after said signal is displayed for restarting the finder to hunt for other called party-lines.

15. Asi automatic switching system according to claim 14 in which certain of the finder brushes connect with the talking conductors of the called line, and said brushes are connected to a jack at said operators position whereby the operator can communicate with the calling subscriber to inform him that the party-line designation dialled by the calling subscriber represents an unassigned party-line station.

16. In an automatic telephone switching sysof the type having a iinal selector with a plurality of party-line stations served by a single set of bank contacts in the selector, means to establish a telephone connection through said selector to a common line leading to said stations, means to apply selective frequency ringing currents to said line, an automatic switch and a party line test mechanism common to a plurality of sets of said bank contacts, said party line test mechanism being controlled by said ringing current transmitted over said automatic switch for determining the condition of said stations, an operators position, and means responsive to the setting of said test mechanism for signalling the operators position when the dialled party-line designation corresponds to one of said stations which is unassigned, and means to extend the calling line to said operators position.

WILLIAM HATTON REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,727,137 Stehlik 1 Sept. 3, 1929 1,738,959 Tharp Dec. 3, 1929 2,309,186 Wallace Oct. 27, 1942 2,224,497 Wright Dec. 10, 1940 2,344,634 Powell Mar. 21, 1944 

